The present invention relates to a stent according to the preamble of claim 1.
Different designs of stents are known from the prior art. These form a vascular prosthesis which consists of a body-tolerated material. Stents are normally used for expanding hollow vessels, such as blood vessels or also body orifices, and for keeping the same in an expanded state. To this end the stent is normally placed in a non-expanded state into a narrow hollow vessel of a patient""s body and is subsequently expanded by suitable means, such as a balloon catheter. Normally, the stent body has a web structure comprising several neighboring web patterns which have adjoining webs and are interconnected by means of connection elements.
A fundamental problem encountered in many stent constructions is that these will shorten upon expansion. Such a shortening, however, is undesired because it cannot be ruled out that the expanded stent due to its shortening no longer covers the entire area inside the vessel or orifice, which area is e.g. to be expanded and supported by the stent.
It is therefore the object of the present invention to provide a stent of the type as outlined in the preamble of claim 1, which stent is flexible in the non-expanded state, builds up sufficient holding forces in the expanded state to remain in said state and reduces its length as little as possible during expansion.
This object is achieved by the features of claim 1.
Since each of the webs of the web patterns comprises three portions that are arranged at an angle relative to one another, this has the effect that upon expansion the angles between the portions will increase, which will minimize or even almost eliminate shrinkage of the stent during expansion.
With such a construction the stent according to the invention is very flexible, preferably in the non-expanded state, such flexibility having a very advantageous effect on the guidability of the stent inside the vessel up to the implantation place, e.g. in the crimped condition on a catheter. Furthermore, the construction according to the invention provides a very stable construction in the expanded state so that the implanted stent can receive great forces, thereby performing an excellent supporting function in the implanted state.
The subclaims relate to advantageous developments of the invention.
Preferably, the portions of each web are made straight.
Furthermore, the webs are subdivided into a central portion and two lateral portions that adjoin the ends of the central portion. The lateral portions preferably enclose obtuse angles with the central portion.
The three portions are preferably arranged relative to one another such that a bowl or plate-like configuration is obtained. Such a configuration, in turn, provides a very compact form during crimping of the stent, as the webs are placed into one another in the manner of plates stacked into one another.
The web patterns are preferably interconnected by connection elements formed as straight webs.
In a particularly preferred embodiment the straight webs extend in a straight line into connection sections of the web patterns which interconnect respectively neighboring webs.
The orientation of the connection elements between two neighboring web patterns is the same. This means that connection elements which are positioned one upon the other have the same orientation. On the other hand, the orientations of the connection elements alternate between two neighboring web patterns so that e.g. when viewing a wall of a stent unwound into the plane one obtains an alternating orientation of the connection elements, once upwards and once downwards.
The stent of the invention has the special advantage that depending on the material used it can be designed either as a self-expanding stent or as a stent which can be expanded by means of a balloon catheter. In both cases its advantageous, previously described characteristics are maintained. If a self-expanding stent is desired, a nickel-titanium alloy should preferably be used as the material.